The present invention relates to a method and apparatus for controlling traffic loading on upstream channels to a cable modem termination system using connection admission control.
In order to provide more products to their subscriber base, cable television companies are offering access to the Internet through their cable modem (CM) boxes. The benefits in using the cable companies instead of a dial-up Internet Service Provider is multiple services under one bill, always-on access, and, in some cases, higher speed access.
In order to provide their customers with Internet access, the cable companies use some of the 50-800 MHZ spectrum typically set aside for their television channels to provide the bandwidth required for the data transfers. A typical cable system has the bandwidth to provide 100 or more television channels to subscribers. Each NTSC television signal requires 6 MHZ of bandwidth.
In order for a cable subscriber to access the Internet through their cable television provider, the subscriber must have a CM. The CM is similar to the Cable Modem Termination System (CMTS) equipment required at the cable company""s headquarters, except for the greater size required at the headquarters. This is to accommodate a greater number of signals than is required by the home modem.
The home CM box and the CMTS use well-known Ethernet frames to communicate between them. The cable system, however, uses a different modulation scheme, Quadrature Amplitude Modulation (QAM), than is normally used in an Ethernet scheme.
Using the QAM modulation, the downstream (from the cable company equipment to the home CM) data rate is in the range of 30-40 Mbps for each 6 MHZ channel. This can accommodate between 500 and 2000 subscribers, The more subscribers that the cable company tries to fit in that spectrum, the lower quality signal for each subscriber results.
The upstream data flow is different and more complex. In the past, cable companies did not have to worry about providing bandwidth for the customer to communicate in the upstream direction. Pay-for-view movies and sports events, however, required this ability. The cable companies therefore, set aside the 5-42 MHZ spectrum to provide the necessary upstream access to the Internet from the home CM.
The world is now on the verge of a revolution that promises to change the way the Internet works and it is guaranteed to change the way the entire world communicates, works and plays. The revolution is the introduction of quality of service (QoS) to the Internet. This QoS revolution is already beginning, because most computer networking products (switches and routers) have already added some type of QoS to their feature sets. Unfortunately, there are many different forms of QoS from which to choose and they are not all compatible with one another. Different standards committees (DiffServ, RSVP, NTLS, etc.) are still deciding which of many different QoS proposals will actually be used in the Internet, and hybrid solutions will likely be developed in the very near future that will enable the QoS revolution.
The change is important, because it will eliminate the current Internet routing model that provides the same xe2x80x9cbest effortxe2x80x9d service to all users, all packets, and all traffic flows. When QoS is enabled in a ubiquitous, end-to-end fashion across the Internet, differentiated services will be permitted, and all packets will be treated differently. High priority packets will be routed with lower latency and lower jitter, while low priority packets may experience more delay and jitter. The throughput needs of each application will determine the priority associated with its corresponding traffic flows, and it is likely that advanced application programs of the future will dynamically change the priority of traffic flows to match the very needs of the user through the entire duration of the session.
Since all packets will not be passed using the same priority level, it follows that all packets cannot be billed using the same charges in the future either. Future Internet users are likely to pay different amounts, for different classes of service, and they may even be billed on a usage basis, e.g., per-minute, per packet, or per byte, similar to the billing schemes used for long distance telephone service today. The use of high priority traffic flow for an application will undoubtedly result in higher Internet usage costs than the use of low priority traffic flows and service level agreements (SLAs) between the Internet user and their service provider will detail the available priority and throughputs in and their associated costs. These changes in the Internet billing model represent an incredible revenue generating potential for access providers that can provide and bill for these new differentiated services, and multiple system operators (MSOs) are key members of this group.
MSOs are positioned in an ideal location within the Internet to play a major role in the QoS revolution, and they will be able to capitalize on the resulting changes. This is because the MSOs are positioned to act as the QoS gatekeeper into the future Internet. They can perform this function because they have access to each subscriber""s service level contract and can appropriately mark the priority of all packets that are injected into the Internet by their subscribers. In fact, the MSOs head end equipment, the cable modem termination system CMTS is actually the first piece of trusted equipment not owned by the subscriber to which subscriber packets must pass on their way to the Internet. The CMTS is positioned at the head end office and it provides basic connectivity between the cable plant and the Internet. FIG. 1 illustrates a simplified cable data system 10 with a CMTS 30. The CMTS 30 is connected through Internet link 40 to the Internet 20. The CMTS 30 is also connected through various cable links 50 to a plurality of subscribers 60.
The MSO also provides customer subscription packages and is able to offer (and bill for) many different subscriber service levels. In addition, if the CMTS equipment permits it, the MSO will also be able to offer dynamic service level upgrades to its subscribers. Features contained within an MSO""s CMTS must provide most of these revenue generating QoS capabilities. This will result in even greater increases in revenues if the MSOs can maintain adequate counts on usage of different services levels consumed by its subscribers.
As set forth above, the CMTS provides basic connectivity between the cable plant and the local area network that interfaces to an edge router on the Internet. The CMTS is responsible for appropriately classifying, prioritizing, flow controlling, queuing, scheduling and shaping all the traffic flows between cable data subscribers and the Internet. As a result, the service provided to cable data subscribers will primarily be determined by the features in the CMTS core.
One important task of the CMTS will be congestion control. If the traffic congestion on upstream channels into the CMTS are not carefully monitored and controlled, information will be lost and subscribers will become dissatisfied with the service.
The invention provides a traffic congestion control solution for use on upstream channels coming into a CMTS using QoS parameters in a connection admission control system. The system first determines the amount of bandwidth available in an upstream channel and then determines how much bandwidth is requested by a subscriber. The system then determines whether or not to accept the subscriber""s request using a connection admission control algorithm.
According to one embodiment of the present invention, a method of controlling traffic loading on a cable modem termination system (CMTS) having a plurality of basic upstream data service flow scheduling types for a cable data system is disclosed. The available bandwidth on an upstream data channel is determined. Data service flow scheduling type of a requesting subscriber is determined. The available bandwidth on the upstream data channel that can be allocated to the data service flow scheduling type is determined. The available bandwidth on an upstream data channel is compared to the bandwidth to be allocated by the CMTS to the requesting subscriber based upon the type of basic upstream data service flow scheduling type to be allocated to the requesting subscriber. It is then determined whether the available bandwidth is greater than, less than or equal to the bandwidth to be allocated by the CMTS to the requesting subscriber for the basic upstream data service flow scheduling type to be allocated for the requesting subscriber. Cable data service to the requesting subscriber is either granted or denied based upon the determination of whether the available bandwidth is greater than, less than or equal to the bandwidth to be allocated to the requesting subscriber.